Release v0.2.0: multiple named API keys per user

Replaces the single per-user DRF token with named, individually-revocable
API keys, so you can run one key per agent and cut off a leaked one without
disrupting the others.

- New ApiKey model (user, name, dbk_-prefixed key, created_at, last_used_at).
  Data migration copies every existing authtoken 1:1 into a "default" named
  key with the same value, so no client (incl. the sibling test project's
  hardcoded test-user key) needs reconfiguring.
- Auth (resolve_token_user) resolves against ApiKey and stamps last_used_at,
  throttled to one write/minute.
- Settings -> API Keys: table with name/key/created/last-used + per-row
  revoke and a create form; keys viewable on demand. Settings -> Account now
  links here; Settings -> Users issues a named initial key.
- Gated provisioning API for test installations: GET/POST /api/keys and
  DELETE /api/keys/{id}, controlled by DAYBOOK_KEY_PROVISIONING_API (unset ->
  follows DEBUG, so off in deployment). Advertised via key_provisioning_api
  in /api/capabilities; 403 when disabled.
- Docs (api/deployment/quickstart/posting-helper), SKILL.md, and env.example
  updated from "token / Settings -> Account" to "key / Settings -> API Keys".
- Tests: new API + UI suites for keys; existing token-based tests moved to
  ApiKey. Full suite 129 passing.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

deploy/env.example

@@ -6,6 +6,11 @@ DJANGO_ALLOWED_HOSTS=localhost,127.0.0.1,your-vm-ip,your-domain.example
 # "CSRF verification failed" because Django can't tell the original request
 # was HTTPS. Set to the public HTTPS origin(s) users actually visit:
 DJANGO_CSRF_TRUSTED_ORIGINS=https://your-domain.example
+# Leave OFF in deployment. When on, POST /api/keys can create/list/revoke API
+# keys over the network (it returns key material), which is only appropriate
+# for automated test installations. Unset, it follows DJANGO_DEBUG — so with
+# DJANGO_DEBUG=0 above it is already off. Set to 1 only on a throwaway test box.
+# DAYBOOK_KEY_PROVISIONING_API=0
 DAYBOOK_DATA_DIR=/data
 DATABASE_PATH=/data/db.sqlite3
 ARTIFACTS_ROOT=/data/artifacts_store